Jim:
I agree with Phil's recommendations on Jeff's book. You can get it
from ARRL. I based my Trylon 64's shunt feed on Jeff's design. The key is
to have something as a capacitive load at or near the tower top to make the
tower appear electrically longer than it is physically. Your Yagi/40M
add-on ought to be a pretty good load.
Many on this reflector would recommend modeling, but I'd say try it and
let us all know. The feed is nothing more than a wire from the bottom of
the tower and connected near the top, keeping it a couple of feet away from
the tower itself (I used PVC tubing as spacer material). Then you feed the
bottom of the wire through a variable transmitting cap of some fairly large
value in series with the coax center; I keep the cap insulated from ground
by mounting it in a plastic weather enclosure (a plastic shoe box from
K-mart). The coax shield gets connected to the tower legs and ground
radials. Tune the cap for min SWR and call CQ.
BTW, the sloper might have an impact on your ability to shunt feed the
tower. If you can't get the tower to load, you might want to remove the
sloper and try again. (I haven't modeled this, so I'm guessing.)
GL es 73 de
Gene Smar AD3F
-----Original Message-----
From: kb9cry@attbi.com <kb9cry@attbi.com>
To: Jim Leahy <jimleahy@adelphia.net>
Cc: Towertalk <towertalk@contesting.com>
To: <towertalk@contesting.com>
Date: Thursday, September 26, 2002 9:17 AM
Subject: Re: [Towertalk] Can my 40' tower be a 160m vertical?
>QSL on all Jim. Purchase Jeff Briggs, K1ZM's book from
>the ARRL titled "DXing on the Edge, The Thrill of 160
>Meters" In it you'll find all the info and hints to
>shunt feed your tower. I did the same (mine's a 72 ft.
>Trylon, but as long at the tower is not too high) and it
>will definately work. You need the vertically
>polarized, low angle signal on topband and you don't get
>that with all the other stuff except a Inverted L, which
>is also in Jeff's book. Piks of my shunt feed can be
>found on my club's website at www.nidxa.org. Go to the
>DX Showcase section. Cu on Topband, 73 Phil KB9CRY
>> Hello all. I've always been under the impression that one had to have a
100'
>> or taller tower in order to shunt feed it for 160m. Therefore, for years
>> I've been fooling with long wires, random wires, low (25') windoms,
slopers
>> etc. without a lot of luck. Plus I'm only running 100w. But I happened
>> across a recent thread where WL7M is using his 40' Rohn on 160/80m. Now
I'm
>> wondering if I can do this with my 40' freestanding tower and get better
>> results with DX. Here's what I have: 40' freestanding tower, Mosley TA-33
>> w/40m kit, 3 phillystran guy wires, each leg to a grounding rod and about
8
>> random length radials buried from the tower base in conjuction with a
W9INN
>> all-band wire sloper. Is this a viable setup for using the tower on160m
>> operation? If so, are there any good books/instructions on exactly how to
do
>> this? I'm also contemplating a Butternut HF2V 80/40 with the 160m kit
which
>> would end up being about 31' in length. Winter will be approaching fast
and
>> I want to get something different going on Top Band. Plus the fact that
I've
>> been inactive for about 3 years, I'm getting itchy! I've worked about
25-30
>> countries with the various wire setups and 100w over the years. Looking
to
>> try something different. I'm currently using a Cushcraft AP8 vertical for
>> 80/40/WARC operation. That antenna, while serving me well when we lived
in
>> an apartment years ago, is really lacking when it comes to 80 meter
>> operation. That is one of the reasons I'm thinking about the Butternut.
>> Bottom line, I REALLY need to improve my 80/160m situation. Thanks for
any
>> help!
>> Jim K2JL
>>
>> _______________________________________________
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